Method of repairing light emitting device, apparatus for repairing light emitting device, and display panel having repaired light emitting device

ABSTRACT

A display panel including a circuit board including first pads, first light emitting devices disposed on the circuit board and including pads, at least one second light emitting device disposed on the circuit board and including pads, metal bonding layers disposed between the pads of the first light emitting devices and the first pads on the circuit board, and a conductive material layer electrically connecting the pads of the second light emitting device to the first pads on the circuit board, in which the conductive material layer includes a conductive portion and a non-conductive portion.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication No. 62/953,399 filed on Dec. 24, 2019, and U.S. ProvisionalPatent Application No. 62/964,440, filed on Jan. 22, 2020, each of whichis hereby incorporated by reference for all purposes as if fully setforth herein

BACKGROUND Field

Exemplary embodiments of the invention relate generally to a method ofrepairing a light emitting device, an apparatus for repairing a lightemitting device, a display panel having the repaired light emittingdevice, and a display apparatus having the same. More particularly,exemplary embodiments of the invention relate generally to a method ofrepairing micro LEDs, an apparatus for repairing micro LEDs, a displaypanel having the repaired micro LEDs, and a display apparatus having thesame.

Discussion of the Background

As an inorganic light source, light emitting diodes have been used invarious fields including displays, vehicular lamps, general lighting,and the like. With various advantages such as long lifespan, low powerconsumption, and rapid response, light emitting diodes have beenreplacing existing light sources in the art.

Meanwhile, conventional light emitting diodes have been mainly used asbacklight light sources in display apparatuses. However, recently,small-sized light emitting diodes, that is, LED display apparatuses thatdirectly implement an image using micro LEDs, have been developed.

In general, a display apparatus realizes various colors through mixtureof blue, green and red light. In order to realize various images, thedisplay apparatus includes a plurality of pixels, each of which includessub-pixels corresponding to blue, green and red light, respectively, inwhich a color of a certain pixel is determined based on the colors ofthe sub-pixels so that images can be realized through combination ofsuch pixels.

LEDs can emit light of various colors depending on their materials, anda display apparatus in which individual micro LEDs emitting blue, green,and red are arranged on a two-dimensional plane, or a display apparatusin which micro LEDs having a stacked structure in which a blue LED, agreen LED, and a red LED are stacked one above another are arranged on atwo-dimensional plane may be provided.

Micro LEDs used in one display apparatus usually require more than onemillion even for a small-sized display. Due to the small size of microLEDs and the enormous number required, mass production of micro LEDdisplay apparatus according to a conventional technology is almostimpossible because of the conventional die bonding technology in whichLED chips are individually mounted. As such, a technology fortransferring a plurality of micro LEDs onto a circuit board in a grouphas been recently developed.

Meanwhile, some of the micro LEDs transferred in a group may exhibitbonding failure or poor luminescence characteristics. These defectivemicro LEDs need to be repaired. Generally, repairment of micro LEDs isto replace defective micro LEDs with favorable micro LEDs, andrepairment of micro LEDs is quite difficult due to the small size of themicro LEDs.

The above information disclosed in this Background section is only forunderstanding of the background of the inventive concepts, and,therefore, it may contain information that does not constitute priorart.

SUMMARY

Methods according to exemplary embodiments of the invention are capableof repairing a light emitting device for a display, particularly microLEDs.

Exemplary embodiments provide an apparatus for repairing a lightemitting device for a display, particularly micro LEDs.

Additional features of the inventive concepts will be set forth in thedescription which follows, and in part will be apparent from thedescription, or may be learned by practice of the inventive concepts.

A display panel according to an exemplary embodiment includes a circuitboard including first pads, first light emitting devices disposed on thecircuit board and including pads, at least one second light emittingdevice disposed on the circuit board and including pads, metal bondinglayers disposed between the pads of the first light emitting devices andthe first pads on the circuit board, and a conductive material layerelectrically connecting the pads of the second light emitting device tothe first pads on the circuit board, in which the conductive materiallayer includes a conductive portion and a non-conductive portion.

The conductive material layer may include at least one of an anisotropicconductive film, an anisotropic conductive paste, and an anisotropicconductive adhesive.

The conductive portion of the conductive material layer may includeconductive balls disposed between the pads of the second light emittingdevice and the pads of the circuit board.

The metal bonding layer may include at least one of AuSn, CuSn, and In.

An upper surface of the second light emitting device may be disposedhigher than those of the first light emitting devices.

Each of the first and second light emitting devices may be configured toemit each of blue light, green light, and red light.

The conductive material layer may contact the first light emittingdevice adjacent to the second light emitting device.

The conductive material layer may be spaced apart from adjacent firstlight emitting devices.

The conductive material layer may have a wider width than that of thecorresponding second light emitting device.

A method of repairing a light emitting device according to anotherexemplary embodiment includes removing at least one defective lightemitting device among a plurality of light emitting devices transferredonto a circuit board, and mounting a second light emitting device at alocation of the circuit board where the defective light emitting deviceis removed using a conductive material layer, in which the conductivematerial layer includes a conductive portion and a non-conductiveportion.

Mounting the second light emitting device may include disposing theconductive material layer at the location of the circuit board where thedefective light emitting device is removed, disposing the second lightemitting device on the conductive material layer, and curing theconductive material layer.

Disposing the second light emitting device may include forming thesecond light emitting device on a substrate, and transferring the secondlight emitting device disposed on the substrate to the conductivematerial layer, and the substrate may be removed from the second lightemitting device after the conductive material layer is cured.

The substrate may include a single second light emitting device.

A plurality of defective light emitting devices on the circuit board maybe repaired using a plurality of substrates each including the singlesecond light emitting devices, respectively.

The method may further include forming bonding material layers on firstpads of the circuit board, respectively, disposing the first lightemitting devices on the bonding material layers, and forming metalbonding layers by applying heat to the bonding material layers.

The defective light emitting device may be removed by applying gas tothe first light emitting device using a gas blower.

The gas blower may apply the gas to the first light emitting device at apredetermined pressure.

The gas may be applied to each of the first light emitting devicestransferred onto the circuit board using the gas blower.

The defective light emitting device may be detected in advance, and thegas may be applied only to the defective light emitting device using thegas blower.

An apparatus for repairing a light emitting device according to yetanother exemplary embodiment includes a first table to support a circuitboard on which first light emitting devices are mounted, a second tableto support a temporary substrate to which second light emitting devicesare adhered, a third table to support a bath including a conductiveadhesive material, and a pickup unit configured to pick up at least oneof the second light emitting devices from the temporary substrate andplace the at least one of the second light emitting devices on thecircuit board.

The pickup unit may include a needle to pick up the second lightemitting device from the temporary substrate.

The needle may have a passage to vacuum-adsorb the second light emittingdevice.

The apparatus may further include a moving device to move the needle inthe vertical direction.

The first, second, and third tables may be configured to move laterallywith respect to the pickup unit.

The apparatus may further include at least one vision device.

The at least one vision device may include a first vision deviceconfigured to be placed over the first, second, and third tables, and asecond vision device configured to be placed under the first, second,and third tables.

The apparatus may further include a display configured to display animage photographed using the vision device.

At least one of the first table and the pickup unit may be configured tovibrate in the lateral direction to separate at least one of the lightemitting devices from the circuit board.

The conductive adhesive material may include at least one of ananisotropic conductive paste and an anisotropic conductive adhesive.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate exemplary embodiments of theinvention, and together with the description serve to explain theinventive concepts.

FIG. 1 shows schematic perspective views of display apparatusesaccording to exemplary embodiments.

FIG. 2 is a schematic plan view of a display panel according to anexemplary embodiment.

FIG. 3 is a schematic enlarged partial cross-sectional view taken alongline A-A′ of FIG. 2 according to an exemplary embodiment.

FIGS. 4A, 4B, 4C, 4D, and 4E are schematic cross-sectional viewsillustrating a process of repairing a light emitting device according toexemplary embodiments.

FIGS. 5A, 5B, 5C, and 5D are schematic cross-sectional viewsillustrating a method of repairing a light emitting device according toan exemplary embodiment.

FIG. 6 is a schematic plan view illustrating light emitting devices forrepairing according to an exemplary embodiment.

FIG. 7 is a schematic plan view of an apparatus for repairing a lightemitting device according to an exemplary embodiment.

FIG. 8 is a schematic cross-sectional view taken along line B-B′ of FIG.7.

FIG. 9 is a schematic cross-sectional view illustrating a process ofremoving a defective device according to an exemplary embodiment.

FIGS. 10A and 10B are schematic cross-sectional views illustrating aprocess of transferring a light emitting device according to anexemplary embodiment.

FIG. 11 is a schematic cross-sectional view illustrating a process ofremoving a defective device according to another exemplary embodiment.

FIG. 12 is a schematic cross-sectional view illustrating a process oftransferring a light emitting device for repairing onto a temporarysubstrate.

FIGS. 13A and 13B are schematic cross-sectional views illustrating aprocess of mounting a light emitting device for repairing on a circuitboard.

FIG. 14 is a schematic plan view illustrating a display panel having alight emitting device for repairing according to an exemplaryembodiment.

FIG. 15 is an enlarged schematic partial cross-sectional view takenalong line C-C′ of FIG. 14.

DETAILED DESCRIPTION

In the following description, for the purposes of explanation, numerousspecific details are set forth in order to provide a thoroughunderstanding of various exemplary embodiments or implementations of theinvention. As used herein “embodiments” and “implementations” areinterchangeable words that are non-limiting examples of devices ormethods employing one or more of the inventive concepts disclosedherein. It is apparent, however, that various exemplary embodiments maybe practiced without these specific details or with one or moreequivalent arrangements. In other instances, well-known structures anddevices are shown in block diagram form in order to avoid unnecessarilyobscuring various exemplary embodiments. Further, various exemplaryembodiments may be different, but do not have to be exclusive. Forexample, specific shapes, configurations, and characteristics of anexemplary embodiment may be used or implemented in another exemplaryembodiment without departing from the inventive concepts.

Unless otherwise specified, the illustrated exemplary embodiments are tobe understood as providing exemplary features of varying detail of someways in which the inventive concepts may be implemented in practice.Therefore, unless otherwise specified, the features, components,modules, layers, films, panels, regions, and/or aspects, etc.(hereinafter individually or collectively referred to as “elements”), ofthe various embodiments may be otherwise combined, separated,interchanged, and/or rearranged without departing from the inventiveconcepts.

The use of cross-hatching and/or shading in the accompanying drawings isgenerally provided to clarify boundaries between adjacent elements. Assuch, neither the presence nor the absence of cross-hatching or shadingconveys or indicates any preference or requirement for particularmaterials, material properties, dimensions, proportions, commonalitiesbetween illustrated elements, and/or any other characteristic,attribute, property, etc., of the elements, unless specified. Further,in the accompanying drawings, the size and relative sizes of elementsmay be exaggerated for clarity and/or descriptive purposes. When anexemplary embodiment may be implemented differently, a specific processorder may be performed differently from the described order. Forexample, two consecutively described processes may be performedsubstantially at the same time or performed in an order opposite to thedescribed order. Also, like reference numerals denote like elements.

When an element, such as a layer, is referred to as being “on,”“connected to,” or “coupled to” another element or layer, it may bedirectly on, connected to, or coupled to the other element or layer orintervening elements or layers may be present. When, however, an elementor layer is referred to as being “directly on,” “directly connected to,”or “directly coupled to” another element or layer, there are nointervening elements or layers present. To this end, the term“connected” may refer to physical, electrical, and/or fluid connection,with or without intervening elements. Further, the D1-axis, the D2-axis,and the D3-axis are not limited to three axes of a rectangularcoordinate system, such as the x, y, and z-axes, and may be interpretedin a broader sense. For example, the D1-axis, the D2-axis, and theD3-axis may be perpendicular to one another, or may represent differentdirections that are not perpendicular to one another. For the purposesof this disclosure, “at least one of X, Y, and Z” and “at least oneselected from the group consisting of X, Y, and Z” may be construed as Xonly, Y only, Z only, or any combination of two or more of X, Y, and Z,such as, for instance, XYZ, XYY, YZ, and ZZ. As used herein, the term“and/or” includes any and all combinations of one or more of theassociated listed items.

Although the terms “first,” “second,” etc. may be used herein todescribe various types of elements, these elements should not be limitedby these terms. These terms are used to distinguish one element fromanother element. Thus, a first element discussed below could be termed asecond element without departing from the teachings of the disclosure.

Spatially relative terms, such as “beneath,” “below,” “under,” “lower,”“above,” “upper,” “over,” “higher,” “side” (e.g., as in “sidewall”), andthe like, may be used herein for descriptive purposes, and, thereby, todescribe one elements relationship to another element(s) as illustratedin the drawings. Spatially relative terms are intended to encompassdifferent orientations of an apparatus in use, operation, and/ormanufacture in addition to the orientation depicted in the drawings. Forexample, if the apparatus in the drawings is turned over, elementsdescribed as “below” or “beneath” other elements or features would thenbe oriented “above” the other elements or features. Thus, the exemplaryterm “below” can encompass both an orientation of above and below.Furthermore, the apparatus may be otherwise oriented (e.g., rotated 90degrees or at other orientations), and, as such, the spatially relativedescriptors used herein interpreted accordingly.

The terminology used herein is for the purpose of describing particularembodiments and is not intended to be limiting. As used herein, thesingular forms, “a,” “an,” and “the” are intended to include the pluralforms as well, unless the context clearly indicates otherwise. Moreover,the terms “comprises,” “comprising,” “includes,” and/or “including,”when used in this specification, specify the presence of statedfeatures, integers, steps, operations, elements, components, and/orgroups thereof, but do not preclude the presence or addition of one ormore other features, integers, steps, operations, elements, components,and/or groups thereof. It is also noted that, as used herein, the terms“substantially,” “about,” and other similar terms, are used as terms ofapproximation and not as terms of degree, and, as such, are utilized toaccount for inherent deviations in measured, calculated, and/or providedvalues that would be recognized by one of ordinary skill in the art.

Various exemplary embodiments are described herein with reference tosectional and/or exploded illustrations that are schematic illustrationsof idealized exemplary embodiments and/or intermediate structures. Assuch, variations from the shapes of the illustrations as a result, forexample, of manufacturing techniques and/or tolerances, are to beexpected. Thus, exemplary embodiments disclosed herein should notnecessarily be construed as limited to the particular illustrated shapesof regions, but are to include deviations in shapes that result from,for instance, manufacturing. In this manner, regions illustrated in thedrawings may be schematic in nature and the shapes of these regions maynot reflect actual shapes of regions of a device and, as such, are notnecessarily intended to be limiting.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this disclosure is a part. Terms,such as those defined in commonly used dictionaries, should beinterpreted as having a meaning that is consistent with their meaning inthe context of the relevant art and should not be interpreted in anidealized or overly formal sense, unless expressly so defined herein.

Hereinafter, exemplary embodiments of the inventive concepts will bedescribed in detail with reference to the accompanying drawings.

FIG. 1 shows schematic perspective views of display apparatusesaccording to exemplary embodiments.

The light emitting device according to an exemplary embodiments may beused in a VR display apparatus such as a smart watch 1000 a or a VRheadset 1000 b, or an AR display apparatus such as augmented realityglasses 1000 c, without being limited thereto.

A display panel for displaying an image is mounted on a displayapparatus. FIG. 2 is a schematic plan view of a display panel 1000according to an exemplary embodiment, and FIG. 3 is a schematic enlargedpartial cross-sectional view taken along line A-A′ of FIG. 2.

Referring to FIGS. 2 and 3, the display panel 1000 includes a circuitboard 110 and light emitting devices 100 and 100 a. The light emittingdevices 100 and 100 a may be small-sized LEDs, commonly referred to asmicro LEDs. For example, the light emitting device 100 may have a sizesmaller than 500 μm×500 μm, and further, smaller than 100 μm×100 μm.However, the inventive concepts are not limited to a particular size ofthe light emitting device 100.

The circuit board 110 may include a circuit for passive matrix drivingor active matrix driving. In an exemplary embodiment, the circuit board110 may include interconnection lines and resistors therein. In anotherexemplary embodiment, the circuit board 110 may include interconnectionlines, transistors, and capacitors. The circuit board 110 may also havepads disposed on an upper surface thereof to allow electrical connectionto the circuit therein.

A plurality of light emitting devices 100 and 100 a is arranged on thecircuit board 110. The light emitting device 100 represents a lightemitting device of good performance mounted on the circuit board 110 bygroup transfer, and the light emitting device 100 a represents arepaired light emitting device. A structure of the light emitting device100 a may be substantially the same as that of the light emitting device100, but the inventive concepts are not limited thereto. An intervalbetween the light emitting devices 100 and 100 a may be at least widerthan a width of the light emitting device 100 or 100 a.

In an exemplary embodiment, the light emitting devices 100 and 100 a maybe sub-pixels that emit light of a specific color, and the sub-pixelsmay form one pixel. For example, a blue LED, a green LED, and a red LEDmay be adjacent to one another to form one pixel. However, the inventiveconcepts are not limited thereto, and each of the light emitting devices100 and 100 a may have a stacked structure emitting light of variouscolors. For example, each of the light emitting devices 100 and 100 amay have a structure in which a blue LED, a green LED, and a red LED arestacked to overlap one another, and thus, one light emitting device 100and 100 a may form one pixel.

The light emitting device 100 may have pads 105, and the pads 105 may beadhered to corresponding pads 115 of the circuit board 110 through abonding layer 120. The bonding layer 120 may be formed by solderbonding, and may include, for example, a metallic bonding material suchas AuSn, CuSn, In, or the like.

The light emitting device 100 a may have pads 105, and the pads 105 maybe adhered to the corresponding pads 115 of the circuit board 110through a conductive material layer 120 a. The conductive material layer120 a includes a conductive portion and a non-conductive portion. Theconductive material layer 120 a may be formed using, for example, ananisotropic conductive film (ACF), an anisotropic conductive paste(ACP), or an anisotropic conductive adhesive (ACA). The light emittingdevice 100 a may be electrically connected to the circuit board 110 byconductive balls 125 in the conductive material layer 120 a.

The conductive material layer 120 a may be in contact with an adjacentlight emitting device 100 as shows, but the inventive concepts are notlimited thereto. In some exemplary embodiments, the conductive materiallayer 120 a may be spaced apart from the light emitting device 100.

In an exemplary embodiment, an upper surface of the light emittingdevice 100 a may be placed higher than that of the light emitting device100. In particular, the conductive material layer 120 a located underthe pads 105 of the light emitting device 100 a may be thicker than thebonding layer 120.

The display panel 1000 may include at least one light emitting device100 a, and the light emitting device 100 a bonded to the circuit board110 by the conductive material layer 120 a may be distinguished from thelight emitting device 100 bonded to the circuit board 110 by the bondinglayer 120, which may include a metallic material.

FIGS. 4A, 4B, 4C, 4D, and 4E are schematic cross-sectional viewsillustrating a process of repairing a micro LED according to exemplaryembodiments.

Referring to FIG. 4A, a circuit board 110 includes pads 115. The pads115 are connected to circuits in the circuit board 110 and providecontact points for connecting a light emitting device 100 to thecircuits. The pads 115 are disposed in each region of the circuit board110 where the light emitting devices 100 are to be mounted to mount aplurality of light emitting devices 100. The pads 115 may be formed of ametal layer including Au. For example, the pads 115 may have amultilayer structure of Cu/Ni/Au.

Barrier layers 121 are provided on the pads 115, and bonding materiallayer 123 is provided on the barrier layer 121. The barrier layers 121may prevent the bonding material layers 123 from diffusing into the pads115, thereby preventing damage to the pads 115. The barrier layer 121may be a metal layer mixed with the bonding material layer 123, or ametal layer for blocking diffusion of the bonding material layer 123.For example, the barrier layer 121 may include at least one of Ni, Cr,Ti, Ta, Mo, and W. For example, the barrier layer 121 may have amultilayer structure of Cr/Ni or Ti/Ni.

The bonding material layer 123 may include AuSn, CuSn, or In. Ingeneral, the bonding material layers 123 are provided on the pads 115for group transfer using micro LED technology. The bonding materiallayer 123 may be formed using, for example, a solder paste includingflux and a metallic material. The bonding material layer 123 may beformed on the pads 115 using, for example, a screen printing technique.

In some exemplary embodiments, a metal layer mixed with the bondingmaterial layer 123 such as an Au layer may be interposed between thebarrier layer 121 and the bonding material layer 123.

The light emitting device 100 has pads 105. The pads 105 correspond tothe pads 115 of the circuit board 110. As shown in the drawing, the pads105 may be bump pads protruding from the light emitting device 100, butin some exemplary embodiments, the pads 105 may not necessarily have aprotruding shape. The plurality of light emitting devices 100 may betransported to correspond to the pads 115 of the circuit board 110.

Referring to FIG. 4B, after the pads 105 of the light emitting device100 are arranged on the bonding material layers 123 as shown in FIG. 4A,a metal bonding layer 120 is formed by applying heat at a bondingtemperature. In particular, the barrier layer 121 and the bondingmaterial layer 123 may be mixed with each other by heat, and at least aportion of the pads 105 may be mixed with the bonding material layer123. In this manner, the light emitting device 100 may be stablyattached to the circuit board 110 by the metal bonding layer 120.

Referring to FIG. 4C, as described with reference to FIG. 4B, once thelight emitting devices 100 are bonded to the circuit board 110, some ofthe light emitting devices 100 having defects may be detected. Suchdefects in the light emitting device 100 may be caused by, for example,bonding failure or by a failure in performance of the light emittingdevice 100.

In this case, a defective light emitting device 100 is removed from thecircuit board 110. The light emitting device 100 having defectivebonding may be removed using a gas blower 300, which will be describedin more detail later with reference to FIG. 5A.

The bonding layer 120 may be removed together with the defective lightemitting device 100, or the remaining bonding layer 120 may beseparately removed using a laser or the like after the defective lightemitting device 100 is removed. As such, the pads 115 may be retained onthe circuit board 110 after the defective light emitting device 100 isremoved. The remaining pads 115 may be substantially the same as thepads 115 before the light emitting device 100 is bonded, but may bedeformed in some cases from the pads 115.

Referring to FIG. 4D, after the defective light emitting device 100 isremoved, a conductive material layer 120 a is formed on the exposed pads115. The conductive material layer 120 a may include conductive balls125. The conductive material layer 120 a may be, for example, ananisotropic conductive film, an anisotropic conductive paste, or ananisotropic conductive adhesive. For example, the conductive materiallayer 120 a may be formed to cover the pads 115 by dispensing theanisotropic conductive paste or the anisotropic conductive adhesive.

Referring to FIG. 4E, a light emitting device 100 a for repairing isdisposed on the conductive material layer 120 a. The light emittingdevice 100 a for repairing is disposed on the conductive material layer120 a so that the pads 105 of the light emitting device 100 a forrepairing match the pads 115 of the circuit board 110. The lightemitting device 100 a for repairing replaces the defective lightemitting device 100, and may have performance required as the lightemitting device 100. Further, the light emitting device 100 a may havesubstantially the same structure as the light emitting device 100, butthe inventive concepts are not limited thereto.

The pads 105 of the light emitting device 100 a are electricallyconnected to the pads 115 of the circuit board 110 by the conductiveballs 125. The light emitting device 100 a may be pressed towards thecircuit board 110, and thus, the conductive balls 125 may electricallyconnect the pads 105 and 115 to each other. The conductive materiallayer 120 a may then be cured.

In general, handling of the light emitting device 100 a is difficult dueto its small size. As such, the light emitting device 100 a may beformed on a substrate 20 a which will be described in more detail later,and then be bonded to the circuit board 110 by handling the substrate 20a. The substrate 20 a may be separated from the light emitting device100 a through a technique, such as laser lift-off, which will also bedescribed in more detail later.

Hereinafter, a method of repairing a micro LED according to exemplaryembodiments will be described in detail.

FIGS. 5A, 5B, 5C, and 5D are schematic cross-sectional viewsillustrating a method of repairing a micro LED according to an exemplaryembodiment.

Referring to FIG. 5A, a display panel 1000 a in which light emittingdevices 100 are transferred onto a circuit board 110 is prepared. Thelight emitting devices 100 may be formed on a wafer and transferred tothe circuit board 110 in a group. The light emitting devices 100 may betransferred to the circuit board 110 using a laser lift-off technique,but the inventive concepts are not limited thereto. Various knownmethods of transferring the light emitting devices 100 onto the circuitboard 110 may be used in other exemplary embodiments.

The display panel 1000 a may be transported to a light emitting deviceremoving apparatus to remove a defective light emitting device. In anexemplary embodiment, the removing apparatus may include a stage 210, agas blower 300, and a camera 400. However, the inventive concepts arenot limited to a particular removing apparatus.

The display panel 1000 a may be placed on the stage 210 and may beclamped to be fixed on the stage 210. The stage 210 may be movable inthe X and Y directions, and may also be movable in the Z direction. Forexample, when the display panel 1000 a is transferred, the stage 210 maymove downwardly in the Z direction to receive the display panel 1000 a,and then move upwardly to remove the defective light emitting device100.

The gas blower 300 may include a needle 310 having a gas outlet, apressure control device 320, and a gas supply pipe 330. The needle 310may have a gas outlet having a small inner diameter so as to blow gastoward the light emitting device 100. For example, the gas outlet mayhave an inner diameter of about 10 μm to about 50 μm.

The pressure control device 320 adjusts a pressure of gas to release gasat a pressure suitable for removing the light emitting device 100 havingfailed bonding.

In an exemplary embodiment, the defective light emitting device may bedetected in advance before being placed in the light emitting deviceremoving apparatus, and the removing apparatus may remove the lightemitting devices 100 determined to have failed bonding. In anotherexemplary embodiment, the light emitting device 100 may be evaluated fora failure in bonding by releasing a gas pressure from the gas blower300. For example, a gas pressure suitable for evaluating the bondingcharacteristics of the light emitting device 100 may be predetermined,and the pressure control device 320 may release gas at a predeterminedpressure through the gas outlet. When gas is released at thepredetermined pressure, the light emitting device 100 having failedbonding is removed while normal light emitting devices 100 are retained.In this manner, a separate process for determining defective lightemitting devices 100 may be obviated.

The gas supply pipe 330 supplies gas to the pressure control device 320from a storage tank storing gas. The gas supply pipe 330 may be aflexible tube to freely move a location of the needle 310, without beinglimited thereto.

In the illustrated exemplary embodiment, gas may be air or an inert gas,and in particular, may be an inert gas, such as He or N₂. The inert gasmay not cause oxidation of a metal bonding layer.

The camera 400 may be disposed to observe the light emitting device 100to which gas is applied from the needle 310. The camera 400 may bedisposed above the light emitting device 100 to capture an image of thelight emitting device 100 on the circuit board 110, but the inventiveconcepts are not limited thereto.

In the illustrated exemplary embodiment, although the stage 210 isexemplarily illustrated and described as being disposed under the gasblower 300 and the camera 400, but the inventive concepts are notlimited thereto. In some exemplary embodiments, the stage 210 may bedisposed above the camera 400 and the gas blower 300

The gas blower 300 applies gas to the light emitting device 100 throughthe needle 310. The gas blower 300 releases gas at a predeterminedpressure using the pressure control device 320 to remove the lightemitting device having failed bonding. In an exemplary embodiment, thegas blower 300 may apply gas only to light emitting devices 100 that aredetermined as defective light emitting devices among the light emittingdevices 100 on the circuit board 110 for the removal. In anotherexemplary embodiment, the gas blower 300 may apply gas to all of thelight emitting devices 100 on the circuit board 110 at a predeterminedpressure and remove the light emitting devices having failed bonding.

The camera 400 observes whether the light emitting device 100 to whichgas is applied by the gas blower 300 is attached or detached from thecircuit board 110. A location where the light emitting device 100 isremoved may be specified using the camera 400. When gas is applied toone light emitting device 100 and removes that light emitting device100, the stage 210 may move in the lateral direction to apply gas toanother light emitting device 100. In this manner, each of the lightemitting devices having failed bonding among the light emitting devices100 on the circuit board 110 may be removed using the gas blower 300.

FIG. 5B shows the circuit board 110 from which the light emittingdevices having failed bonding are removed. When the defective lightemitting devices 100 are removed, a metal bonding layer 120corresponding thereto may also be removed while the corresponding pads115 may be retained on the circuit board 110 at locations where thelight emitting devices 100 have been removed.

Referring to FIG. 5C, a conductive material layer 120 a is disposed atthe location where the light emitting device 100 is removed, and a lightemitting device 100 a for repairing is disposed thereon. The lightemitting device 100 a for repairing may be formed on a substrate 20 a,and the light emitting device 100 a may be disposed at a desiredlocation by handling the substrate 20 a. The substrate 20 a may be agrowth substrate for growing an epitaxial layer. For example, thesubstrate 20 a may be a sapphire substrate, a silicon substrate, a GaAssubstrate, or the like. The light emitting devices 100 a may bemanufactured using epitaxial layers grown on the substrate 20 a, and mayinclude a first conductivity type semiconductor layer, an active layer,and a second conductivity type semiconductor layer. Furthermore, thelight emitting devices 100 a may have a structure in which a pluralityof LEDs is stacked.

A plurality of light emitting devices 100 may be removed from thecircuit board 110, the conductive material layer 120 a may be disposedat each of the locations where the light emitting devices 100 areremoved, and the substrates 20 a on which the light emitting devices 100a are formed may be disposed thereon, respectively. According to anexemplary embodiment, one light emitting device 100 a may be formed onone substrate 20 a, and thus, the substrates 20 a are spaced apart fromeach other.

The light emitting device 100 a for repairing may be pressed against thecircuit board 110, and thus, pads 105 of the light emitting devices 100a and pads 115 on the circuit board 110 may be electrically connected.

The conductive material layer 120 a may be cured by heat, and thus, thelight emitting devices 100 a may be adhered to the circuit board 110.

After the conductive material layer 120 a is cured, the substrate 20 amay be separated from the light emitting device 100 a using the laserlift-off technique or the like. The display panel 1000 is completed asshown in FIG. 5D by separating each of the substrates 20 a from thelight emitting devices 100 a.

In the illustrated exemplary embodiment, although the conductivematerial layers 120 a disposed on the circuit board 110 to correspond tothe light emitting devices 100 a are exemplarily described as beingsimultaneously cured, the inventive concepts are not necessarily limitedthereto. For example, in some exemplary embodiments, each of thedefective light emitting devices 100 on the circuit board 110 may beindividually repaired by repeatedly performing a process of mounting thelight emitting device 100 a to the location where the defective lightemitting device 100 is removed using each substrate 20 a having thelight emitting device 100 a for repairing.

In the illustrated exemplary embodiment, an upper surface of the lightemitting device 100 a for repairing mounted on the circuit board 110 maybe placed higher than that of the light emitting device 100. As such,damage to the light emitting devices 100 that have already been mountedon the circuit board 110 by the substrate 20 a may be prevented.However, the inventive concepts are not limited thereto, and in someexemplary embodiments, elevations of upper surfaces of the lightemitting devices 100 and 100 a may be substantially the same.

A region between the light emitting devices 100 and 100 a may be filledwith a light reflecting material or a light blocking material such, as ablack matrix, to prevent light interference between the light emittingdevices 100 and 100 a. In this case, the conductive material layer 120 amay be disposed under the light blocking material.

FIG. 6 is a schematic plan view of light emitting devices 100 a forrepairing according to an exemplary embodiment.

Referring to FIG. 6, a plurality of light emitting devices 100 a forrepairing may be formed on a wafer 20. The light emitting device 100 afor repairing may be formed by forming epitaxial layers on a substrate20 a and patterning the epitaxial layers. A process of forming the lightemitting device 100 a for repairing is generally similar to that offorming the light emitting device 100, and thus, the light emittingdevices 100 a may have substantially the same or similar structure asthat of the light emitting device 100. In an exemplary embodiment, thelight emitting device 100 a may have a structure including a singleactive layer to form one sub-pixel. In another exemplary embodiment, thelight emitting device 100 a may have an LED stacked structure havingmultiple active layers, and thus, may form one pixel.

The wafer 20 may be divided into a plurality of sections, and eachsection may include a single light emitting device 100 a. The lightemitting device 100 a has a smaller size than the corresponding section,and thus, the substrate 20 a of each section has a relatively largewidth compared to the light emitting device 100 a.

The substrate 20 a may have a size suitable for handling, and thus, thelight emitting device 100 a may be easily attached to the circuit board110 using the substrate 20 a. In addition, the light emitting device 100a may be easily transferred from the substrate 20 a onto the circuitboard 110 without damaging normal light emitting devices 100 mounted onthe circuit board 110. As described above, the substrate 20 a isseparated from the light emitting device 100 a during mounting processusing a technique such as laser lift-off.

FIG. 7 is a schematic plan view of an apparatus 10 for repairing a lightemitting device according to an exemplary embodiment, and FIG. 8 is aschematic cross-sectional view taken along line B-B′ of FIG. 7.

Referring to FIGS. 7 and 8, the apparatus 10 may include a first table11, a second table 13, a third table 17, a bath 19, and a first visiondevice 23 a, a second vision device 23 b 23 b, first and second displays33 a and 33 b, a work station 51, a circuit board 110, a temporarysubstrate 130, and a pickup unit 150. The pickup unit 150 may include amoving device 21, a header 23, a needle 25, and an absorption pipe 27.

The work station 51 provides a space for carrying out a repairingoperation of a light emitting device. The first, second, and thirdtables 11, 13, and 17 may be laterally and/or vertically movable on thework station 51. The first, second, and third tables 11, 13, and 17, forexample, may be movable in the lateral direction (x, y direction) usinga lateral direction moving part, and movable in the vertical direction(z direction) using a vertical direction moving part.

The first table 11 may move back and forth in the lateral direction, forexample, in the x direction. The circuit board 110 on which the lightemitting devices 100 are mounted may be disposed on the first table 11.The first table 11 may be movable so that the circuit board 110 can beplaced under a lower portion of the needle 25 of the pickup unit 150, orthe circuit board 110 can be spaced far apart from the lower portion ofthe needle 25 of the pickup unit 150.

The first table 11 may also be movable in the vertical direction, thatis, in the z direction, so that an elevation of the first table 11 maybe adjusted.

The second table 13 may move back and forth in the lateral direction,for example, in the x direction. The temporary substrate 130 on whichlight emitting devices 100 a for repairing are mounted may be disposedon the second table 13. The second table 13 may be movable so that thetemporary substrate 130 can be placed under the lower portion of theneedle 25 of the pickup unit 150, or the temporary substrate 130 can bespaced far apart from the lower portion of the needle 25 of the pickupunit 150.

The second table 13 may also be movable in the vertical direction, thatis, in the z direction, and thus, an elevation of the second table 13may be adjusted.

The third table 17 may move back and forth in the lateral direction, forexample, in the y direction. The bath 19 containing a conductiveadhesive material may be disposed on the third table 17. The third table17 may be movable so that the bath 19 can be placed under the lowerportion of the needle, or the bath 19 can be spaced far apart from thelower portion of the needle 25.

The third table 17 may also be movable in the vertical direction, thatis, in the z direction, and thus, an elevation of the third table 17 maybe adjusted.

The circuit board 110 is disposed on the first table 11. The lightemitting devices 100 are disposed on the circuit board 110. The lightemitting devices 100 are mounted on the circuit board 110 by grouptransfer, and the circuit board 110 is disposed on the first table 11with the light emitting devices 100 mounted thereon.

Some of the light emitting devices 100 mounted on the circuit board 110are removed from the circuit board 110 due to failures in bonding,electrical, and/or optical properties. As such, some regions of thecircuit board 110 may have empty space by removing the defective lightemitting device 100.

The apparatus 10 is operated to place the light emitting device 100 afor repairing at a location where the defective light emitting device100 has been removed. When all of the defective light emitting devices100 are replaced with the light emitting devices 100 a for repairing,the circuit board 110 is transported from the first table 11 and a newcircuit board 110 may be disposed on the first table 11.

The temporary substrate 130 is disposed on the second table 13. Thelight emitting devices 100 a for repairing are disposed on the temporarysubstrate 130. The light emitting devices 100 a for repairing may betransferred from a growth substrate onto the temporary substrate 130using a technique such as laser lift-off. The temporary substrate 130may include an adhesive material layer. The adhesive material layer maybe, for example, an ultraviolet (UV) tape that may be cured by UVirradiation. The adhesiveness of the adhesive material layer may bereduced to, for example, about 1/100 or less when cured. After the lightemitting devices 100 a for repairing are transferred onto the temporarysubstrate 130, the adhesive material layer may be cured to facilitateseparation of the light emitting devices 100 a for repairing from thetemporary substrate 130 by reduced adhesiveness of the adhesive materiallayer.

The bath 19 is disposed on the third table 17. The bath 19 may contain aconductive adhesive material for bonding the light emitting device 100 afor repairing to the circuit board 110. The conductive adhesive materialmay be, for example, an anisotropic conductive paste (ACP) or ananisotropic conductive adhesive (ACA).

The first vision device 23 a may be disposed over the work station 51.The first vision device 23 a observes a location where the needle 25 isoperated, and whether the circuit board 110, the temporary substrate130, or the bath 19 is accurately disposed under the needle 25. Thelocation of the light emitting device 100 on the circuit board 110 orthe location of the light emitting device 100 a on the temporarysubstrate 130 may be confirmed through the first vision device 23 a.

The first vision device 23 a may include a camera to photograph anobject to be observed, and a photographed image may be checked throughthe first display 33 a.

The second vision device 23 b may be disposed to face the needle 25. Thesecond vision device 23 b may be disposed under the work station 51, andthe work station 51 may include a groove for placing the second visiondevice 23 b.

The second vision device 23 b is disposed under the needle 25, andobserves whether the needle 25 and the circuit board 110, or the needle25 and the temporary substrate 130 are accurately arranged. The needle25 may be arranged with the light emitting device 100 a on the temporarysubstrate 130 to pick up the light emitting device 100 a, and may alsobe arranged in a recovery space on the circuit board 110 to place thepicked-up light emitting device 100 a in an empty space on the circuitboard 110. To this end, the second vision device 23 b may provide avisual assistance to ensure proper placement of the needle 25.

For example, the second vision device 23 b may include a camera tophotograph an object to be observed, and a photographed image may bechecked through the second display 33 b.

The first and second displays 33 a and 33 b display the imagesphotographed by the first and second vision devices 23 a and 31 b. Inthis manner, a user may visually check an operation state of the needle25 using the displays 33 a and 33 b.

The circuit board 110 is disposed on the first table 11. The circuitboard 110 may be laterally transported relative to the pickup unit 150by lateral movement of the first table 11. In another exemplaryembodiment, the pickup unit 150 may be laterally movable rather than thefirst table 11.

The circuit board 110 may include the light emitting devices 100 mountedby group transfer. In this case, some of the light emitting devices 100mounted on the circuit board 110 may have mounting failure or defectiveelectrical and optical properties. As such, the circuit board 110 may betransported to the apparatus 10 to replace the defective light emittingdevices 100 with light emitting devices 100 a for repairing.

When each of the defective light emitting devices 100 is replaced withthe light emitting devices 100 a for repairing, a display panel (2000 inFIG. 14) including the light emitting devices 100 a for repairing andthe light emitting devices 100 is provided.

The temporary substrate 130 is disposed on the second table 13. Thetemporary substrate 130 may be laterally transported relative to thepickup unit 150 by lateral movement of the second table 13. In anotherexemplary embodiment, the pickup unit 150 may be laterally movablerather than the second table 13.

The temporary substrate 130 supports the light emitting devices 100 afor repairing. The temporary substrate 130 may include an adhesivematerial layer, such as a UV tape, and the light emitting devices 100 afor repairing are attached to the adhesive material layer and supportedby the temporary substrate 130.

The pickup unit 150 picks up the light emitting device 100 a forrepairing from the temporary substrate 130 and mounts the light emittingdevice 100 a for repairing on the circuit board 110. The moving device21 causes the needle 25 to move upward and downward, and to this end,the moving device 21 a step motor, for example. In an exemplaryembodiment, the moving device 21 may move the needle 25 in the lateraldirection.

The header 23 may be used to mount the needle 25, and is attached to themoving device 21 to move upward and downward by the moving device 21.

The needle 25 is operated to pick up the light emitting device 100 a onthe temporary substrate 130 and place the light emitting device 100 a ata predetermined location on the circuit board 110. In an exemplaryembodiment, the needle 25 may vacuum-adsorb the light emitting device100 a, and may detach the light emitting device 100 a from the temporarysubstrate 130 using a vacuum-absorption force. To this end, the needle25 may include a passage for vacuum-absorption.

The light emitting device 100 a adsorbed by the needle 25 is at leastpartially immersed in the conductive adhesive material in the bath 19,and is thereafter bonded to pads of the circuit board 110. When thelight emitting device 100 a is bonded onto the circuit board 110, theneedle 25 is separated from the light emitting device 100 a. The needle25 may be easily separated from the light emitting device 100 a byinjecting gas into the passage for vacuum-absorption.

The absorption pipe 27 is used to vacuum-exhaust the passage in theneedle 25. The absorption pipe 27 may be connected to the moving device21 or may be connected to the header 23. An absorption passage of theabsorption pipe 27 is connected to the passage of the needle 25, andthus, when the needle 25 is disposed on an upper surface of the lightemitting device 100 a, the passage of the needle 25 may bevacuum-exhausted and the light emitting device 100 a may bevacuum-adsorbed.

In the illustrated exemplary embodiment, although the needle 25 isexemplarily described as adsorbing the light emitting device 100 a usingvacuum-absorption, the inventive concepts are not limited thereto. Insome exemplary embodiments, in addition to vacuum-absorption, the needle25 may pick up the light emitting device 100 a and detach the lightemitting device 100 a from the temporary substrate 130 using variousknown techniques.

Hereinafter, an operation of the apparatus 10 according to an exemplaryembodiment will be described in more detail. In particular, a processfor forming a display panel 2000 a, and a process for removing thedefective light emitting device from the display panel 2000 a will bedescribed. Subsequently, a process of providing the light emittingdevices 100 a for repairing on the temporary substrate 130, and aprocess for replacing the defective light emitting devices with thelight emitting devices 100 a for repairing replace using a conductiveadhesive material will be described.

FIG. 9 is a schematic cross-sectional view illustrating a process ofremoving a defective device according to an exemplary embodiment.

Referring to FIG. 9, the display panel 2000 a including a circuit board110 on which light emitting devices 100 are mounted is prepared. Thelight emitting devices 100 may be formed on a wafer and transferred tothe circuit board 110 in a group. The light emitting devices 100 may betransferred to the circuit board 110 using a laser lift-off technique,but the inventive concepts are not limited thereto. In other exemplaryembodiments, various known methods for transferring the light emittingdevices 100 onto the circuit board 110 may be used. The process ofbonding the light emitting device 100 to pads of the circuit board 110will be described in more detail later with reference to FIGS. 10A and10B.

The display panel 2000 a may be placed in a light emitting deviceremoving apparatus to remove a defective light emitting device. Theremoving apparatus is not particularly limited, and various knownapparatuses to remove the defective light emitting device may be used.In an exemplary embodiment, the removing apparatus may include a stage210, a gas blower 300, and a camera 400.

The display panel 2000 a may be placed on the stage 210 and may beclamped to be fixed on the stage 210. The stage 210 may be movable inthe X and Y directions, and may also be movable in the Z direction. Forexample, when the display panel 2000 a is transported, the stage 210 maymove downwardly in the Z direction to receive the display panel 2000 a,and thereafter, move upwardly to remove the defective light emittingdevice 100.

The gas blower 300 may include a needle 310 having a gas outlet, apressure control device 320, and a gas supply pipe 330. The needle 310may have a gas outlet having a small inner diameter so as to blow gastoward the light emitting device 100. For example, the gas outlet mayhave an inner diameter of about 10 μm to about 50 μm.

The pressure control device 320 adjusts a pressure of gas to release gasat a pressure suitable for removing the defective light emitting device100.

In an exemplary embodiment, whether the light emitting device 100 isdefective may be detected in advance before being placed in the lightemitting device removing apparatus, and the removing apparatus mayremove the light emitting devices 100 determined to have failed bonding.In another exemplary embodiment, the light emitting device 100 may beevaluated for a failure in bonding by releasing a gas pressure from thegas blower 300. For example, a gas pressure suitable for evaluating thebonding characteristics of the light emitting device 100 may bepredetermined, and the pressure control device 320 may release gas at apredetermined pressure through the gas outlet. When gas is released atthe predetermined pressure, the light emitting device 100 having failedbonding is removed while normal light emitting device 100 are retained.

The gas supply pipe 330 supplies gas to the pressure control device 320from a storage tank storing gas. The gas supply pipe 330 may be aflexible tube to freely move a location of the needle 310, without beinglimited thereto.

In the illustrated exemplary embodiment, gas may be air or an inert gas,and in particular, may be an inert gas, such as He or N₂. The inert gasmay not cause oxidation of a metal bonding layer.

The camera 400 may be disposed to observe the light emitting device 100to which gas is applied from the needle 310. The camera 400 may bedisposed above the light emitting device 100 to capture an image of thelight emitting device 100 on the circuit board 110, but the inventiveconcepts are not limited thereto.

In the illustrated exemplary embodiment, although the stage 210 isexemplarily illustrated and described as being disposed under the gasblower 300 and the camera 400, but the inventive concepts are notlimited thereto. In some exemplary embodiments, the stage 210 may bedisposed above the camera 400 and the gas blower 300.

The gas blower 300 applies gas to the light emitting device 100 throughthe needle 310. The gas blower 300 releases gas at a predeterminedpressure using the pressure control device 320 to remove the lightemitting device having failed bonding. In an exemplary embodiment, thegas blower 300 may apply gas only to light emitting devices 100 that aredetermined as defective light emitting devices among the light emittingdevices 100 on the circuit board 110 for the removal. In this manner,since gas is not applied to each of the light emitting devices 100, aprocess time may be shortened. In another exemplary embodiment, the gasblower 300 may apply gas to all of the light emitting devices 100 on thecircuit board 110 at a predetermined pressure and remove the lightemitting devices having failed bonding.

The camera 400 observes whether the light emitting device 100 to whichgas is applied by the gas blower 300 is attached or detached from thecircuit board 110. A location where the light emitting device 100 isremoved may be specified using the camera 400. When gas is applied toone light emitting device 100 and removes that light emitting device100, the stage 210 may move in the lateral direction to apply gas toanother light emitting device 100. In this manner, each of the lightemitting devices having failed bonding among the light emitting devices100 on the circuit board 110 may be removed using the gas blower 300.

Once each of the defective light emitting devices 100 are removed, thecircuit board 110 may be placed on the first table 11 of the apparatus10 described above.

FIGS. 10A and 10B are schematic cross-sectional views illustrating aprocess of transferring a light emitting device according to anexemplary embodiment.

Referring to FIG. 10A, a circuit board 110 includes pads 115. The pads115 are connected to circuits in the circuit board 110, and providecontact points for connecting the light emitting device 100 to thecircuits. The pads 115 are disposed in each region of the circuit board110 where the light emitting devices 100 are to be mounted. The pads 115may be formed of a metal layer including Au. For example, the pads 115may have a multilayer structure of Cu/Ni/Au.

Barrier layers 121 are provided on the pads 115, and a bonding materiallayer 123 is provided on the barrier layer 121. The barrier layers 121may prevent the bonding material layers 123 from diffusing into the pads115, thereby preventing damage to the pads 115. The barrier layer 121may be a metal layer mixed with the bonding material layer 123, or ametal layer for blocking diffusion of the bonding material layer 123.For example, the barrier layer 121 may include at least one of Ni, Cr,Ti, Ta, Mo, and W. For example, the barrier layer 121 may have amultilayer structure of Cr/Ni or Ti/Ni.

The bonding material layer 123 may include AuSn, CuSn, or In. Ingeneral, the bonding material layers 123 are provided on the pads 115for group transfer using micro LED technology. The bonding materiallayer 123 may be formed using, for example, a solder paste includingflux and a metallic material. The bonding material layer 123 may beformed on the pads 115 using, for example, a screen printing technique.

In some exemplary embodiments, a metal layer mixed with the bondingmaterial layer 123 such as an Au layer may be interposed between thebarrier layer 121 and the bonding material layer 123.

The light emitting device 100 has pads 105. The pads 105 correspond tothe pads 115 of the circuit board 110. As shown in the drawing, the pads105 may be bump pads protruding from the light emitting device 100, butin some exemplary embodiments, the pads 105 may not necessarily have aprotruding shape. By group transfer, the plurality of light emittingdevices 100 may be transported to correspond to the pads 115 of thecircuit board 110.

Referring to FIG. 10B, after the pads 105 of the light emitting device100 are arranged on the bonding material layers 123 as shown in FIG.10A, a metal bonding layer 120 is formed by applying heat at a bondingtemperature. In particular, the barrier layer 121 and the bondingmaterial layer 123 may be mixed with each other by heat, and at least aportion of the pads 105 may be mixed with the bonding material layer123. In this manner, the light emitting device 100 may be stablyattached to the circuit board 110 by the metal bonding layer 120. Inthis case, a support substrate used to transfer the light emittingdevices 100 to the circuit board 110 is removed from the light emittingdevices 100, and thus, the display panel 2000 a described in FIG. 9 maybe provided.

FIG. 11 is a schematic cross-sectional view illustrating a process ofremoving a defective device according to another exemplary embodiment.In the illustrated exemplary embodiment, a pickup unit 150 of anapparatus 10 is used to remove the defective light emitting device.

Referring to FIG. 11, a display panel 2000 a having the defective lightemitting device 100 may be directly disposed on a first table 11.Whether the light emitting device 100 is defective or not may bedetermined in advance, and the defective light emitting device 100 maybe placed under a needle 25 by lateral movement of the first table 11.The needle 25 may be placed above the defective light emitting device100 by the movement of the moving device 21, and vacuum-adsorb thedefective light emitting device 100.

Once the needle 25 is in close contact with the defective light emittingdevice 100, the defective light emitting device 100 may be separatedfrom the circuit board 110 by vibrating the first table 11 or the needle25 in the lateral direction. Subsequently, the needle 25 may discard thedefective light emitting device 100 by lifting the defective lightemitting device 100 in a vacuum-adsorbed state.

According to the illustrated exemplary embodiment, since the apparatus10 removes the defective light emitting device 100 and mount the lightemitting device 100 a for repairing, a process of repairing the lightemitting device may be further simplified.

FIG. 12 is a schematic cross-sectional view illustrating a process oftransferring a light emitting device 100 a for repairing onto atemporary substrate 130.

Referring to FIG. 12, the light emitting devices 100 a may be formed ona substrate 101. The substrate 101 may be a growth substrate for growingan epitaxial layer, for example, a sapphire substrate, a GaAs substrate,a silicon substrate, a GaN substrate, or a SiC substrate, but theinventive concepts are not limited thereto. The substrate 101 may bedivided into a plurality of sections having a predetermined size, andthe light emitting devices 100 on each section may be transferredtogether to the temporary substrate 130.

The light emitting device 100 a according to the illustrated exemplaryembodiment may have the same size and structure as those of the lightemitting device 100 described above. The light emitting devices 100 and100 a may have, for example, sizes smaller than 500 μm×500 μm, andfurther, smaller than 100 μm×100 μm, which are known in the art asmini-LEDs or micro-LEDs according to their sizes. In an exemplaryembodiment, the light emitting devices 100 and 100 a may be sub-pixelsthat emit light of a specific color, and the sub-pixels may form onepixel. For example, a blue micro LED, a green micro LED, and a red microLED may be disposed adjacent to one another to form one pixel. In thiscase, the substrate 101 is used to form micro LEDs for emitting light ofa specific color. In another exemplary embodiment, each of the lightemitting devices 100 and 100 a may have a stacked structure that emitslight of various colors. For example, each of the light emitting devices100 and 100 a may have a structure in which a blue LED, a green LED, anda red LED are stacked to overlap one another, and thus, each one of thelight emitting devices 100 and 100 a may form one pixel.

The temporary substrate 130 according to an exemplary embodiment may bea light-transmitting substrate. The temporary substrate 130 may includean adhesive material layer on a surface thereof. The adhesive materiallayer may be a material layer that may have varying adhesiveness uponcuring. For example, the adhesiveness of the adhesive material layer maybe reduced when cured. According to an exemplary embodiment, theadhesive material layer may be an ultraviolet tape (UV) tape. When theultraviolet tape is cured by UV irradiation, the adhesiveness thereofmay be reduced to about 1/100 or less, further to about 1/200 or less.For example, the adhesiveness of the adhesive material layer may beabout 100 gf/mm before curing, and may be about 0.5 gf/mm after curing.

The light emitting devices 100 a on the substrate 101 are attached tothe temporary substrate 130 having an uncured adhesive material layer.Each of the light emitting devices 100 a on the substrate 101 may beattached to the temporary substrate 130 by the adhesive material layer.

Subsequently, the substrate 101 is removed from the light emittingdevices 100 a using a technique, such as laser lift off (LLO) or thelike. The adhesive material layer may prevent locations of the lightemitting devices 100 a from being changed while the substrate 101 isseparated using laser lift-off. After the substrate 101 is removed, thetemporary substrate 130 is placed on a second table 13 of the apparatus10 with the light emitting devices 100 a attached thereon.

Referring back to FIGS. 7 and 8, the temporary substrate 130 disposed onthe second table 13 may be transported to the lower portion of theneedle 25 by lateral movement of the second table 13. The needle 25picks up the light emitting device 100 a from the temporary substrate130. When the needle 25 picks up the light emitting device 100 a, thesecond table 13 moves in the lateral direction and returns back to anoriginal location.

Subsequently, the third table 17 moves laterally to the lower portion ofthe needle 25. The needle 25 moves downward to cause at least a portionof the light emitting device 100 a contact the conductive adhesivematerial in the bath 19 on the third table 17. As such, the conductiveadhesive material is attached to a lower surface of the light emittingdevice 100 a.

Subsequently, the third table 17 returns back to an original location bylateral movement, and the first table 11 moves laterally to place thecircuit board 110 under the lower portion of the needle 25. Inparticular, a region of the circuit board 110 from which the defectivelight emitting device 100 has been removed is placed under the needle25. Subsequently, the needle 25 moves downward to place the lightemitting device 100 a on the circuit board 110. The needle 25 may pressthe light emitting device 100 a against the circuit board 110, and thus,the light emitting device 100 a may be attached to the circuit board 110by a conductive adhesive material. Subsequently, the needle 25 releasesthe light emitting device 100 a, and thus, the light emitting device 100a is transferred onto the circuit board 110.

A process of moving the light emitting devices 100 a from the temporarysubstrate 130 to the circuit board 110 using the needle 25 may becontinuously carried out, and thus, the light emitting devices 100 a mayreplace each of the defective light emitting devices 100. In thismanner, the display panel 2000 in which the light emitting devices 100and the defective light emitting devices 100 a are arranged together isprovided.

FIGS. 13A and 13B are schematic cross-sectional views illustrating aprocess of mounting a light emitting device for repairing on a circuitboard according to another exemplary embodiment.

Referring to FIG. 13A, after the defective light emitting device 100 isremoved, pads 115 may be retained on the circuit board 110. The retainedpads 115 may be substantially identical to the pads 115 before the lightemitting device 100 is bonded, but may be deformed from the pads 115.

The needle 25 adsorbs the light emitting device 100 a for repairing, anddips the light emitting device 100 a into the bath 19, so that a portionof the conductive adhesive material, that is, a conductive materiallayer 120 a is attached on the light emitting device 100 a. Theconductive material layer 120 a may have conductive balls 125 in aninsulating matrix, and may be, for example, an anisotropic conductivepaste or an anisotropic conductive adhesive (ACA).

Referring to FIG. 13B, the needle 25 moves downward and presses thelight emitting device 100 a against the circuit board 110, so that thelight emitting device 100 a is attached to the circuit board 110 by theconductive material layer 120 a. By pressing the light emitting device100 a, a portion of the conductive material layer 120 a may protrude tothe outside of the light emitting device 100 a.

The conductive balls 125 may be disposed between the pad 105 of thelight emitting device 100 a and the pad 115 of the circuit board 110,and the light emitting device 100 a and the circuit board 110 may beelectrically connected by the conductive balls 125. The conductivematerial layer 120 a may be cured by heat, and the apparatus 10 mayinclude a heating unit for curing the conductive material layer 120 a.

After the conductive material layer 120 a is cured, the needle 25releases the light emitting device 100 a. By repeating this process,each of the defective light emitting devices 100 on the circuit board110 may be replaced with the light emitting devices 100 a for repairing,and thus, the display panel 2000 of FIG. 14 may be provided.

FIG. 14 is a schematic plan view illustrating a display panel 2000having a light emitting device for repairing according to an exemplaryembodiment, and FIG. 15 is an enlarged schematic partial cross-sectionalview taken along line C-C′ of FIG. 14.

Referring to FIGS. 14 and 15, the display panel 2000 includes a circuitboard 110 and light emitting devices 100 and 100 a. The light emittingdevices 100 and 100 a may be small-sized LEDs, commonly referred to asmicro LEDs. For example, the light emitting device 100 may have a sizesmaller than 500 μm×500 μm, and further, smaller than 100 μm×100 μm.However, the inventive concepts are not limited to a particular size ofthe light emitting devices 100 and 100 a.

The circuit board 110 may include a circuit for passive matrix drivingor active matrix driving. In an exemplary embodiment, the circuit board110 may include interconnection lines and resistors therein. In anotherexemplary embodiment, the circuit board 110 may include interconnectionlines, transistors, and capacitors. The circuit board 110 may also havepads disposed on an upper surface thereof to allow electrical connectionto the circuit therein.

A plurality of light emitting devices 100 and 100 a is arranged on thecircuit board 110. The light emitting device 100 represents a lightemitting device of good performance mounted on the circuit board 110 bygroup transfer, and the light emitting device 100 a represents a lightemitting device for repairing. A structure of the light emitting device100 a may be substantially the same as that of the light emitting device100, but the inventive concepts are not limited thereto. An intervalbetween the light emitting devices 100 and 100 a may be at least widerthan a width of the light emitting device 100 or 100 a.

In an exemplary embodiment, the light emitting devices 100 and 100 a maybe sub-pixels that emit light of a specific color, and the sub-pixelsmay form one pixel. For example, a blue LED, a green LED, and a red LEDmay be adjacent to one another to form one pixel. However, the inventiveconcepts are not limited thereto, and each of the light emitting devices100 and 100 a may have a stacked structure emitting light of variouscolors. For example, each of the light emitting devices 100 and 100 amay have a structure in which a blue LED, a green LED, and a red LED arestacked to overlap one another, and thus, one light emitting device 100and 100 a may form one pixel.

The light emitting device 100 may have pads 105, and the pads 105 may beadhered to corresponding pads 115 of the circuit board 110 through abonding layer 120. The bonding layer 120 may be formed by solderbonding, and may include, for example, a metallic bonding material suchas AuSn, CuSn, In, or the like.

The light emitting device 100 a may have pads 105, and the pads 105 maybe adhered to the corresponding pads 115 of the circuit board 110through a conductive material layer 120 a. The conductive material layer120 a includes a conductive portion and a non-conductive portion. Theconductive portion electrically connects the pads 105 to the pads 115,and the non-conductive portion surrounds the conductive portion. Theconductive material layer 120 a may be formed using, for example, ananisotropic conductive paste (ACP) or an anisotropic conductive adhesive(ACA). The light emitting device 100 a may be electrically connected tothe circuit board 110 by conductive balls 125 in the conductive materiallayer 120 a. The conductive material layer 120 a according to theillustrated exemplary embodiment may occupy a wider width than that ofthe light emitting device 100 a, as shown in the drawings. However, theconductive material layer 120 a formed according to the illustratedexemplary embodiment does not significantly deviate from a region of thelight emitting device 100 a, and thus, may be spaced apart from adjacentlight emitting devices 100.

In an exemplary embodiment, an upper surface of the light emittingdevice 100 a may be placed higher than that of the light emitting device100. In particular, the conductive material layer 120 a located underthe pads 105 of the light emitting device 100 a may be thicker than thebonding layer 120. However, the inventive concepts are not limitedthereto, and the upper surface of the light emitting device 100 a may beplaced at the same elevation as that of the upper surface of the lightemitting device 100, or may be placed lower than that of the uppersurface of the light emitting device 100.

The display panel 2000 may include at least one light emitting device100 a, and the light emitting device 100 a bonded to the circuit board110 by the conductive material layer 120 a may be distinguished from thelight emitting device 100 bonded to the circuit board 110 by the metalbonding layer 120.

The display panel 2000 may be mounted in various types of displayapparatuses to display an image. The display panel 2000 may be used in aVR display apparatus such as a smart watch, a VR headset, or an ARdisplay apparatus such augmented reality glasses, without being limitedthereto.

Although certain exemplary embodiments and implementations have beendescribed herein, other embodiments and modifications will be apparentfrom this description. As such, the inventive concepts are not limitedto such embodiments, but rather to the broader scope of the appendedclaims and various obvious modifications and equivalent arrangements aswould be apparent to a person of ordinary skill in the art.

What is claimed is:
 1. A display panel, comprising: a circuit boardincluding first pads; first light emitting devices disposed on thecircuit board and including pads; at least one second light emittingdevice disposed on the circuit board and including pads; metal bondinglayers disposed between the pads of the first light emitting devices andthe first pads on the circuit board; and a conductive material layerelectrically connecting the pads of the second light emitting device tothe first pads on the circuit board, wherein the conductive materiallayer includes a conductive portion and a non-conductive portion.
 2. Thedisplay panel of claim 1, wherein the conductive material layer includesat least one of an anisotropic conductive film, an anisotropicconductive paste, and an anisotropic conductive adhesive.
 3. The displaypanel of claim 2, wherein the conductive portion of the conductivematerial layer includes conductive balls disposed between the pads ofthe second light emitting device and the pads of the circuit board. 4.The display panel of claim 1, wherein the metal bonding layer includesat least one of AuSn, CuSn, and In.
 5. The display panel of claim 1,wherein an upper surface of the second light emitting device is disposedhigher than those of the first light emitting devices.
 6. The displaypanel of claim 1, wherein each of the first and second light emittingdevices is configured to emit each of blue light, green light, and redlight.
 7. The display panel of claim 1, wherein the conductive materiallayer contacts the first light emitting device adjacent to the secondlight emitting device.
 8. The display panel of claim 1, wherein theconductive material layer is spaced apart from adjacent first lightemitting devices.
 9. The display panel of claim 8, wherein theconductive material layer has a wider width than that of thecorresponding second light emitting device.
 10. A method of repairing alight emitting device, comprising: removing at least one defective lightemitting device among a plurality of light emitting devices transferredonto a circuit board; and mounting a second light emitting device at alocation of the circuit board where the defective light emitting deviceis removed using a conductive material layer, wherein the conductivematerial layer includes a conductive portion and a non-conductiveportion.
 11. The method of repairing a light emitting device of claim10, wherein mounting the second light emitting device includes:disposing the conductive material layer at the location of the circuitboard where the defective light emitting device is removed; disposingthe second light emitting device on the conductive material layer; andcuring the conductive material layer.
 12. The method of repairing alight emitting device of claim 11, wherein: disposing the second lightemitting device includes: forming the second light emitting device on asubstrate; and transferring the second light emitting device disposed onthe substrate to the conductive material layer; and the substrate isremoved from the second light emitting device after the conductivematerial layer is cured.
 13. The method of repairing a light emittingdevice of claim 12, wherein the substrate includes a single second lightemitting device.
 14. The method of repairing a light emitting device ofclaim 13, wherein a plurality of defective light emitting devices on thecircuit board is repaired using a plurality of substrates each includingthe single second light emitting devices, respectively.
 15. The methodof repairing a light emitting device of claim 10, further comprising:forming bonding material layers on first pads of the circuit board,respectively; disposing the first light emitting devices on the bondingmaterial layers; and forming metal bonding layers by applying heat tothe bonding material layers.
 16. The method of repairing a lightemitting device of claim 14, the defective light emitting device isremoved by applying gas to the first light emitting device using a gasblower.
 17. The method of repairing a light emitting device of claim 16,wherein the gas blower applies the gas to the first light emittingdevice at a predetermined pressure.
 18. The method of repairing a lightemitting device of claim 17, wherein the gas is applied to each of thefirst light emitting devices transferred onto the circuit board usingthe gas blower.
 19. The method of repairing a light emitting device ofclaim 17, wherein: the defective light emitting device is detected inadvance; and the gas is applied only to the defective light emittingdevice using the gas blower.
 20. An apparatus for repairing a lightemitting device, comprising: a first table to support a circuit board onwhich first light emitting devices are mounted; a second table tosupport a temporary substrate to which second light emitting devices areadhered; a third table to support a bath including a conductive adhesivematerial; and a pickup unit configured to pick up at least one of thesecond light emitting devices from the temporary substrate and place theat least one of the second light emitting devices on the circuit board.21. The apparatus for repairing a light emitting device of claim 20,wherein the pickup unit includes a needle to pick up the second lightemitting device from the temporary substrate.
 22. The apparatus forrepairing a light emitting device of claim 21, wherein the needle has apassage to vacuum-adsorb the second light emitting device.
 23. Theapparatus for repairing a light emitting device of claim 21, furthercomprising a moving device to move the needle in the vertical direction.24. The apparatus for repairing a light emitting device of claim 20,wherein the first, second, and third tables are configured to movelaterally with respect to the pickup unit.
 25. The apparatus forrepairing a light emitting device of claim 20, further comprising atleast one vision device.
 26. The apparatus for repairing a lightemitting device of claim 25, wherein the at least one vision deviceincludes: a first vision device configured to be placed over the first,second, and third tables; and a second vision device configured to beplaced under the first, second, and third tables.
 27. The apparatus forrepairing a light emitting device of claim 25, further comprising adisplay configured to display an image photographed using the visiondevice.
 28. The apparatus for repairing a light emitting device of claim20, wherein at least one of the first table and the pickup unit isconfigured to vibrate in the lateral direction to separate at least oneof the light emitting devices from the circuit board.
 29. The apparatusfor repairing a light emitting device of claim 20, wherein theconductive adhesive material includes at least one of an anisotropicconductive paste and an anisotropic conductive adhesive.